I mentioned this on the test page, I simply didn't have a modern 7200RPM 2.5" drive on hand (only older 7200RPM 2.5" drives which were slower than the 5400.6) while I was conducting these tests. As I put together the data for our HDD bench I will add them in though :)

Between the 5400.6 and the WDVR you should be able to get a good idea of where this thing falls though.

Yeah, the one thing though is that having, say, a normal Momentus 7200 would allow us to tell if the NAND is really offering us a benefit over a drive without it, and if so, what percentage performance increase can be attributed to it.

I understand you didn't have the drive at this time, but if you could update this article in the future, it would be much appreciated.Reply

The issue with that line of thinking is that this drive is not just HDD+SSD, the algorithms that the drive uses to read and write data is on a vastly different ball field. This drive is an HDD with SSD capabilities and sometimes benefits.

Until everyone understands that, they (consumers) will expect SSD performance at least some of the time, which is a result of poor understanding. Of course, after all the technical articles on SSDs and as a result HDDs, I'm amazed that people would ever expect any SSD performance from a HDD with flash. The flash is just like nitrous in a car; a 100 shot doesn't offer 100hp, but maybe 60hp instead. A good poke, but not the real thing.Reply

That's a terrible metaphor. A "100 shot" of nitrous is called a "100 shot" because it's good for 100 horsepower. Dyno tests on properly tuned vehicles repeatedly confirm that the advertised power change is usually within a few HP of the documentation.

Now that I think about it, I guess it's inadvertently a good metaphor for poorly understanding technology. :)

In any event, you have a good point that it's deceptive to market this as a "hybrid". It's just a regular drive with a large intelligent cache. They should just say "now! with adaptive caching!" or something.Reply

What I'm curious about is how this drive handles regularly used files that change somewhat often. Caching can be great for executables or libraries (DLLs, etc), given that they don't change often if at all. But what happens when you have files that are accessed during a specific task that may change every time you perform this task? You said that the algorithm doesn't work with writes, which if it understood what write was coming in, it could intercept and possibly alter the already cached data to the new value.

This mostly came from a nerdy WoW example where while textures and such don't normally change too often, add-on settings can possibly change every time you load the game (and load-up can be pretty ardruous with a lot of add-ons). So, if these settings files are changing possibly every time, the cache values will be out of date and it'll have to use its poor Random Read rate to access the proper data.

It's really just one drop in the bucket of the many examples you can think of where this drive wouldn't have a problem, but start-up time in WoW is one of the reasons why I went with the Intel X25-M to begin with... when I bought it, it was pretty much top notch in random read performance.Reply

As is the case with any cache there has to be some mechanism to invalidate data in the cache if the original data is modified. I believe that's what happens here. There's a table of LBAs that are cached and if one is modified then the cached version is immediately invalidated and/or updated.

"the Momentus XT however, the SLC NAND acts exclusively as a read cache - writes never touch the NAND."

and considering that it meant that the caching wouldn't access incoming writes for validating cached data. It sounded odd that way as it'd make caching an absolute sleeping bear of a problem. I'm assuming the statement is meant to be taken literally -- the drive simply doesn't write cache to help speed up writes.

Thanks for the clarification on a sleepy Monday morning and bienvendo!Reply

Anand, how do you think this would compare if they chose to do, say 8GB of MLC instead of 4GB of SLC? Surely it would bring the cost down, and I would think the double cache would be more important than the decrease in speed?Reply

Most SSDs use wear leveling algorithms or compression or some other fairly complicated mechanism to ensure reliability. Seagate wanted to make this as simple as possible while still being reliable.Reply

Here is a request for a test. What happens in dual-boot scenarios? If I boot into Windows 7 and then lets say into Ubuntu, then I expect the drive will have some trouble determining what to cache in its relatively small 4GB NAND.Reply

"The drive looks at access patterns over time (most likely via a history table of LBAs and their frequency of access) and pulls some data into the NAND. If a read request comes in for an LBA that is present in the NAND, it's serviced out of the 4GB chip. If the LBA isn't present in the NAND, the data comes from the platters."

it works at an very low level at LBAbelow is simplifiedif LBA 50 is accessed say 2 times or more it then gets added to the flash if LBA 50 is over written it invalidates the LBA 50 block from the flash (its bit more then what i have say but basically what it does)

this drive does not talk to the OS at all when putting stuff onto the flash it makes an history of what parts of the disk are accessed the most and puts it on the flash (FIle or not)

the disk does not care what OS is running as its only looking at the History of the LBA access on the hdd side of this drive, so there should no issues using these drives in raid as it works at the LBA level of whats accessed the most

even better as each drive has 4gb of cache on them and raid 0 spreads data across muti disks the flash can be 4gb x N1 so if you have 4 XT drives you have 16gb of read cache flash available so if you open or use upto 16gb of files/LBA blocks that norm never change and are in use often they be cached so most of the reads come from the flash and Writes would goto the disk (if an Write and read are going on often the spinning disk maybe often only Writing most of the time as the reads would come from the flash)Reply

The hard drive's firmware controls what gets cached. If you went back and forth between two OS's, you'd probably end up with either one or neither of them cached. The article explains that the best case scenario for a hybrid drive is where your most frequently used applications can fit within the 4GB of flash memory. Reply

While I know you prefer the discrete SSD+RAID solution, there's something to be said for simplicity (from an end user perspective; at least.) I would personally love to see a 1TB drive with around 32 GB of NAND for around $200. Given that both 1TB drives and 32GB SSDs are available for under a bill, this should be doable, right?

And on a different note; I'd be interested in seeing how a similar drive with a much larger flash cache performs in an enterprise scenario. Would the sync algorithm kill performance? Or would a larger cache allow wear leveling to make up for an increase in IOPS?Reply

32GB of SLC would push the price of such a drive beyond $400 once manufacturer’s margins are taken into account with current generation flash. If MLC could be used instead, the price might be pushed down into the $250 range for your hypothetical drive, but it would have to cache data far less frequently to avoid wearing out the flash (or have to include a real SSD-like controller and some extra flash as spare area, once again driving up the price).Reply

I just put this drive in my 15" MacBook Pro. There is a slight increase, but it's very very slight. What I think you'll notice more over the OEM drive is the noise. When the fans are off, and I'm in a quiet room, normally my MBP makes nearly no noise. I can hear this Momentus' platter spinning. It's not obnoxious, bad, but you will notice it if you're in a quiet room.Reply

It's due to the fact that it's a mechanical drive with moving parts. At some times the head might be positioned closer to the data requested resulting in improved performance whereas other times it may have to wait for the next revolution to come to the same data. This creates slight variations in performance.Reply

I don't think that makes sense. The second and third runs are consistently faster than the first run, and relatively consistent with each other. What causes a purely mechanical hard drive to learn?Reply

Actually, I was thinking about comparing this hybrid drive to Windows' own methodology of clustering frequently used data on a USB Flash drive (ReadyBoost, is it?). Granted, USB Flash is not as fast as this on-board SLC, and as far as I understand ReadyBoost is using USB Flash for lower latency purposes only. Yet, from what I hear ReadyBoost helps quite a bit in the OS boot process.

But then I've noticed this reply indicating that SuperFetch was NOT disabled in any of the tests. Well, that pretty much invalidates all results obtained in the tests, don't you think? With 4GB of RAM, SuperFetch overrides much of 4GB of read-only NAND cache, and most likely confuses the cache controller. Have the test configuration had 8GB (or more) RAM, the situation would have been much worse still.

Is there a possibility to redo the same tests with SuperFetch turned OFF? That would be a synthetic benchmark for Windows Vista and Windows 7 users, but it will be closer to reality for Windows XP, Windows Server and non-Windows users.Reply

you need to disable the ready boot or ready boost (i got to go out now so not going to check logs to what is doing the boot optimization) as i see 400mb or so of ram been free up after 20-30 secs after desktop is shownReply

Does SuperFetch play the same role on the Momentus XT? Is someone were running WinXP, would we then expect the boot times to be about the same as the Velociraptor, and both of these have the same boot times no matter how many times you rebooted?Reply

vista and windows 7 make an cache file so when it boots up it loads it into ram so when the programs request it its all ready in ram, it norm frees up approx 400MB on my system once the desktop has shown for more then 20-30 secs

the above can only be done after the first boot has happened (so second and 3rd boot are norm better as it now has history and this fie is remade every boot so the flash is likely not been used as its an new file every boot up as it tweeks it every boot)

superfetch and this preboot in windows 7 would of messed some of these results up an littleReply

There's not much point in the synthetic benchmarks besides showing how the drive performs on applications that you're not running frequently--i.e. to compare the hdd-minus-the-4gb-flash-cache performance of the drive, basically.

I'd say these hybrid drives are the best of both worlds and hence the best drives currently on the market. Capacity plus speed at "little" more than a standard magnetic drive. AwesomeReply

I really wish they could have used 8-16GB of FLASH. 4GB isn't enough to really speed up everything you use allot on your computer to SSD speeds. I think for most people 8-16GB could definitely nail down the common stuff.

What would be really sweet is if some company would make a hybrid drive controller that could take a SSD and HDD, then slave them together and make a hybrid system. Then I could select the size SSD and HDD based on my performance requirements.Reply

Seagate can only do what makes them money. If they sell a lot of these then the design team will be allowed to continue improving and exploring additional options. If they dont sell well, well...

What I want is a flash cache that stores all my 4K random writes in flash, and also stores in flash any 4K cluster that I access frequently. 16GB 4 channel MLC would cost about the same as 1 channel of 4GB SLC. But they would need to add wear leveling.Reply

the idea of the drive is so that the Most common read LBA blocks on the disk get cached into the flash, the drive does not care if the Read was an file or not as its only looking at what Part of the disk was read the most and puts that onto the flash

It would be interesting to see how this SSD/HDD "do-it-yourself" hybrid fairs against The Mighty Anandtech Storage Benchmark, and, if pairing a fast SSD with a fast HDD, would give us a truly seamless best of both worlds experience.Reply

I have a quick question: Does this drive constantly spin up and spin down to save power? The reason I ask is because this puts a lot of wear on the mechanical drive.. so I would stay away from this drive if that is the case.

I still wonder why no drive manufacturer has tried to pair 60-80GB of flash with a mechanical drive and combine it into one 2.5" package. Instead of having a hybrid drive like this, I would rather have one Flash partition for my OS and apps, and one partition on the mechanical drive for the rest of my data. This would be useful for laptops, which usually only have one drive bay. Obviously the two "drives" would have to share the SATA bus, but I think the advantages would outweigh the disadvantages.

Core i3-350M, 5400 RPM 2.5" HDD, clean Windows 7 - and I get ~30 seconds from power button to web browser (~22 seconds if I would install "Boot Cooler", but that's not the point). You, on the other hand, get ~50 seconds on "partial" boot sequence (no POST, no web browser) and much more powerful CPU. It definitely looks like Windows 7 ReadyBoot (successor to "regular" WinXP boot prefetch) did not have enough time to learn. So this does not look like real-life comparison.Reply

The Tom's Hardware review was almost a polar-opposite of Anand's. They performed a number of tests but did not include what I think is absolutely crucial to the intended purpose of this drive: the Boot Time vs. # of runs. I don't know what they intended to extract from all of their tests, as the base storage media of this drive is mechanical, not flash. Therefore, it comes as no surprise that the XT performed almost on-par with the vanilla version of the Momentus 7200.4 in many of their tests.Reply

I for one would certainly alspo like to see RAID 0 and 1 results. I would suspect that this Momentus XT drive would benefit similiar to RAID as traditional harddrives, but it would be nice to have it confirmed.Reply

Compared to the Seagate Momentus 5400.6 the XT uses considerable more power. ... What this means is that depending on your workload you might see worse notebook battery life with the Momentus XT compared to a mainstream drive.

Since when is a third of a Watt at idle, three-quarters of a Watt at load, "consider[ably] more power"?

With most notebooks nowadays having a 40 Watt-hour batteries or higher, an increase of one Watt won't exactly kill battery life. And that's assuming it's going constantly at full power.Reply

Thumbs up to seagate for the sollution, the one used in previous hybrids that relied on the OS was not very effective.I actually made a thread on XS forum a couple of months back discussing a sollution like this, a HDD with a NAND read-only cache using LBA read pattern mapping as caching algorithm.In my discussion, i suggested using 8-16GB (1-2 dual plane dies) MLC ONFI 2.x NAND on a single channel for lower complexity. This would give up to about 7500 4KB random read IOPS (30MB/s), and 90-180MB/s sequential read (for cache hits). At a cost of roughly 2-3$/GB + a NAND controller, the added price tag would be around 25-50$.I think this could be interresting for higher capacity 3,5" "black" drives as well as high-performance high capacity notebook HDDs.Reply

Hybrid HD seems similar to Intel Turbo Boost technology, in terms of both SSD capacity and NAND type, except that Turbo Boost allows certain level of control such as caching only data accessed some pre-given programs. Any idea how these two compare in terms of performance?Reply

It would be interesting to compare performance of hybrid SSD with software-based flash read cache schemes. There are basically two of them for Windows: built-in Readyboost and third-party eBoostr. Other operating systems have even better mechanisms, eg. Solaris has L2ARC caching scheme for reads and ZIL for writes.

Both Windows caching mechanisms can work with either USB sticks, or memory cards in built-in readers. Second option is very interesting as it means SLC flash cards can be used.

I suspect hardware controlled read-cache as implemented in this hybrid drive will totally beat Windows software -based mechanism in one important application: running virtual machines. It's because hardware cache operates on disk blocks so it doesn't matter it these blocks are from base machine or virtual machine, while software Windows mechanisms rely on file-based statistics, so they only speed up base machine. One would have to create separate cache for each VM to get speedup. Btw. software-based Solaris caching doesn't have this limitation. Reply

I don't think writing through the ssd is that important, as it can be effectively cached using the main memory of the system. Only for sustained writes >1 Gb this would become slow if the caching works well.Reply

I would add $50 to buy X25-M 80GB and $50 more for external 250GB WD Passport, and that would make me happier :) I'm already using X25-M in my desktop for about a year and I'm not going down for any hybrid, SSD only as a system drive.Reply

All this seems to be doing in the same thing as the almost universally panned readyboost. Microsoft even had a spec for this called readydrive, and Intel had robson.

If they enabled Readyboost on a PCIE or SATA drive, you could likely get this same performance (or better) by adding a low capacity SSD to your system. What would happen if you dedicated a small SSD to a pagefile btw? Does Windows persistently store page file information between boots, thus using it to speed boot times?Reply

Not really. Seagate decides what to cache based on disk block level. This is much more universal approach than file-statistics-based readyboost, as it allows to cache most frequently used blocks from large files, like virtual machine virtual disks or those giant *.dat files of games. Readyboost is good to speed up access to lots of small files, like *.dll *.ini or small exe, but is no good for extracting most used blocks of large files. Reply

You said that power would be equal or lesser to most HDDs, and I was wondering if that was do to the power used x time taken to complete w/e? Most charts showed the power consumption higher than the 5400.6 which could be a pretty average notebook HDD, but the time to boot up and what-not were much lower for the H-HHD. Just trying to figure out if watts/sec average would be lower and allow more battery life?

I've been very pleased with your wait-and-see approach to most new technologies from the SSD front. So I was a bit shocked to see a glowing recommendation without the disclaimer to wait and see what happens in the next couple of months. This is potentially a great notebook drive (honestly for desktops a real SSD + mechanical HD is vastly superior but yes more expensive), but until we see some firmware updates and/or issues with the drive I think it should remain a recommendation with a major warning.

Currently 4GB is being limited simply because of Software problem ( 64Bit OS Required ) rather then Hardware, We can already make single stick 4GB DDR3 cheaply, only the market is not there yet. When 64Bit reaches tipping point, ( 1 - 2 years time ), 4GB System would be minimum with 8GB or even 16GB system. With So much RAM we could cache those Random Read Write Directly to RAM. Why would would need a Hybrid HDD?

" With So much RAM we could cache those Random Read Write Directly to RAM. Why would we need a Hybrid HDD?"

I think what is confusing you is the differences between RAM and Flash. RAM stores data while constantly consuming power. When the power is cut the data is lost. Flash retains the data when power is cut. It is also much slower than RAM in terms of read/write performance (RAM drives have been a geeks dream for a couple years now but the costs are still quite prohibitive. It seemed like we were getting closer to being possible for the average tech geek without a trust fund when RAM prices were so low last year but due to the recent price hikes it's again out of reach).

So to answer your question IMO this drive is designed for a laptop computer where you only have a single HD bay and power consumption is a significant issue. In a laptop situation it is not practical to use RAM as a cache since you'd be draining the battery even when the computer is off. Reply

Anand I think you are missing important advantages of and SSD in a laptop, (1) lower power consumption than that of a traditional drive with spinning platters and more importantly (2) decreased susceptibility to catastrophic data loss due to a hard drive crash when one's computer is dropped or undergoes any other rapid acceleration and deceleration. As this last consideration happens all to often with laptops, it seems to me that an SSD drive should be standard issue in most, if not all laptops. A hybrid drive will not provide this protection.Reply

Hybrid drives are probably one of the most pointless technologies of the last give years. I don't see how they will ever amount to much. The only way they will is if the cache becomes massive, about the size of what SSDs are now and has a smarter caching algorithm. I can do the same thing that they are doing with their hybrid drive with windows already. Just plop in 8GB of RAM & set windows to prefer system caching. Bam, whatever ram you're not using is used as a cache for reads & that memory can always be reclaimed by programs needing to use it.

Hybrid drives only have the negatives of SSD(cost) with the negatives of HDDs(speed, reliability, noise, power consumption), without much of the benefit. Whoever thought "hey, put some flash on it and then we'll let the HDD spin down!', great idea when the hard drive takes probably about 0.5 seconds in good scenario to boot back up, but some could take a couple seconds. Not a good user experience. Boot times look nice, but who spends their time rebooting their computer all day? Is 30 extra seconds booting going to be worth the added cost?

Maybe Seagate should focus efforts on a "dual drive" where you get a 32GB SSD & a 500GB HDD combined into a a single 2.5" form factor. That would let people use the 32GB as their OS drive & the 500GB for their large files, etc.Reply

Normal HDD write speed, and very good read speed the second time for small files.

For that purpose, this drive is very good and the 4GB is not that bad because only small files are cached, though I would have hoped for at least double that. There is no mention of how small the file needs to be in order to be cached, or maybe I misunderstood the article.

This drive faces two challenges:1- Just one NAND chip so no parallel read so limited read speed of about 30-40 GB p/s2- The NAND is used only for reads, so the write speed is not accelerated.

I'm not going to fuss a lot about the write, but I hope they make a version with say 2*4GB chips and a controller to raid the reads, I would be happy to shell some extra hard earned money for that.Reply

It's not a "Smart Hybrid" like what was being proposed earlier, with Windows Vista/7 being able to identify it as being a hybrid drive and optimize your experience by placing the most used files into the flash cache. It's as "Dumb Hybrid" essentially the flash is just another layer on top of the normal in-memory buffer. Play a large video file a couple times and all your program files are flushed from the cache, just due to the amount of data going back and forth and since the cache is "dumb" it doesn't know if the sectors it's caching are part of an important document or some image from Temporary Internet Files.

It may not be bad if you have small needs, but I think a lot of enthusiasts would be disappointed with it.Reply

I agree with all his comments.This is a good hybrid HDD, but to laptops only since the price premium is $50 to $90 which is quite expensive. For the same price or little more for the desktop, we can buy an SSD and HDD with a lot more performance and capacity.

For his recommendation, this is still a good drive for notebook users looking for more capacity and performance since SSD's, though perfect for the application, is too expensive and lack capacity. Don't doubt the reliability since writes and storage are done on the platters, same reliability with mechanical HDD.

Lastly, I think the 4GB size of SLC NAND flash is chosen as the least (expensive SLC) amount of memory for the most often used files or blocks (typical usage - OS, common Apps). Adding more or making it twice bigger will only benefit users with more and varied apps. It can be done with dual channel but the performance improvement will not be as great. Simply, Seagate just wants more margins and less trouble.Reply

I hate to burst peoples' bubbles here but how many of the files slowing down boot are going to stay in the 4GB cache? Assuming you spend more of your time running your computer and working with other files that get loaded and unloaded more often than core startup components (somewhat questionable with Windows, I realize ;), then the only time you'll see boot speedup is in artificial tests. Of course, that's the way you should want it...Reply

As I said: all files up to 256k (512B - 256k) can be stored on the 4GB Module. I don't think that the firmware moves bigger files onto the NAND, because it is a waste of space and a waste of performance gain (there is nearly no gain).

Just check it with JDiskReport for example. On my system (windows 7 x64, many programs, some games on partition C, install is ~8 months old) all files from 0-256k together make up about 3GB of space.

So again: 4GB should be enough for most users to store EVERY smaller file (256k is rather big).Reply

If you want to speed up Windows boot - you do not need neither SSD nor hybrid HDD. Just install and configure Boot Cooler (www.bootcooler.com). It is free. But it is beta. And it will not accelerate application launches after Windows boot.Reply

I think SF-1200 SSDs controller (with its new free space tweak) are affordable compared to other SSDs prices,Intel which is one of the cheapest and better ones cost 225 for 80 GB, and this one cost 200 for 60 GB.SF-1200 SSDs are just 18,4% more expensive than intel's alternative.Reply

Interesting article, but I still have no idea of my HP Mini netbook (2 GB RAM) would benefit at all from this drive. Considering the CPU is a *huge* bottleneck, I just wonder if anything would feel snappier with this drive? For now, I must keep searching....Reply

I would like to know if a SSD helps loading web pages. If true, this also would hurt this hybrid kind of drive, because maybe lots of small files used only once could be stored in the flash memory.Reply

It definitely does, but I cannot provide numbers.I had a Hitachi 5400rpm in my laptop (~2 years old). I changed to a UltraDrive ME (GX) about 16 months ago. And the pages load definitely faster. I always had a feeling, that the HDD limited somehow web page loading, because I really heard how stressful this really is to a slow HDD.

Again, no numbers here, but they load definitely faster if you used a slow/old HDD before (don't think that there is any difference with fast 7200rpm HDDs).Reply

sounds like a nice project for bored engineers, but I personally hate hybrid anything. its there to just delay the inevitable and/or milk the old as long as possible, while at best complicating the overall system and increasing potential failure points.

Interesting, Amazon (pre-order) and Newegg (ETA 6/1) listings for these drives are already undercutting the prices Anand posted by a good $20-ish... Newegg lists the 500GB drive at $130 and Amazon is offering pre-orders on the 320GB at like $115. If Seagate maintains that aggressive pricing they could certainly displace the low end SSD market for a while...

I'm still happy with the X25-V on my netbook but I'm the sort that doesn't mind carrying an external drive on a long trip. You really gotta wonder why hybrid drives like this haven't shown up earlier, from a technical standpoint they seem simpler than any SSD (no need for TRIM, etc.).Reply

I'd really like to see you compare two desktop 3.5" drives, 7200rpm 32MB cache drives to this drive. Then stripe RAID them together and compare that RAID to this one drive. Then RAID two of these together and compare it to the two desktop drives in RAID. Basically, I'm gonna set up a striped RAID on my desktop, I wanna know if I'd be better off using two 3.5" all mechanical drives or if I should go for two of these hybrid drives. 1TB is plenty for me.Reply

Great article and this looks like a winner for any performance laptop. However, it would be good to see a comparison with a 7200RPM drive instead of 5400RPM since anyone considering this would rather see that comparison. At least I would. Would it be worth updating my exsiting Seagate 500GB 7200RPM HDD for one of these?Reply

I'm going to replace the optical drive in my Macbook Pro with a HDD and am not sure if I should go SSD + Mechanical or get two of these and stripe RAID it?

How do you think the RAID performance of two Momentus XT would be? That way you'd have 8GB of NAND right, so... a bit more "SSD like" I suspect? The cost for that would be 260 US... not bad for 1TB of fast storage in a laptop...

Comments from you and others on this would be much appreciated, cheers!Reply

I honestly hope these things sell like hot cakes just to send a message to drive makers that INNOVATION is something people want and are willing to pay a little more for. I will seriously consider one of these for my existing laptop, as well as a budget way to get WDVR performance on my desktop.

I have to disagree with your recommendation of this technology, unless you are constantly rebooting your system you are better off just using the RAM cache. Do people really reboot that much? I typically only need to reboot every couple months (basically for security updates in the kernel). Even my laptops just use sleep mode.

With only 4GB of read-only cache, you might as well just buy RAM. On the other hand, if they made the flash size large enough that it wasn't affordable to purchase the same amount of RAM, or if they allow write caching, this hybrid technology would be worth while.Reply

Umm.. I do! The allure of the faster boot time has caused me to retrofit all of my Mac g5's as well as laptops with sdd tech. I am in recording, so I can tell you with certainty that waiting for the damn rig to reboot with a room of testy people is nerve wracking at best. With audio programs one is always moving from one to the other all the time to get at all of the different attributes in the myriad of different programs. They all quarrel with each other for the rights to the audio hardware, thereby requiring a reboot. Over and over . All day long. Ya I guess you could manually switch the iac buss but that only works half the time. This technology is a godsend to artists and engineers like me. If you can afford one( ssd) it will revolutionize your workflow. I currently run a 240 SSD as my native drive. Logic takes up 60 gig. Protools takes it's share and before you know it, you are close to the edge with respect to reserve space. Enter Momentus. This is where all of the rest of my sample libraries are stored. Maybe it's a POS. I will let you know, right after I restart this thing.Reply

"most likely via a history table of LBAs and their frequency of access"

I don't think so. If you look at the number of LBs that exist, it is freaking HUGE --- even if you cluster at, say, 4KB clusters, on a 500GB drive you have about 125 million of these and that's still a not insubstantial amount of RAM --- and an array which then has to be ordered dynamically to do anything useful.

The way I would handle this is to treat the thing like a CPU cache with sets and ways. If we treat it as non-associative, then we have each block of cache (whether a "block" is 512 bytes or 4KB) corresponds to ~128 blocks of disk. The absolute dumbest way to do things is that, for each block, as the block is read, if it's not in the cache it's put in it's appropriate single pre-ordained place --- like a simple-minded 1-way cache.

But of course that's the dumbest way of doing things. Much better would be to make the cache 4 or 8 way wide, and for each way to store an LRU to MRU ordering (or the various tricks CPU designers have used to fake this), then when a block is read that is not in the cache, we toss the oldest block in the cache and store the newly read block.

BUT, and this is important, this is STILL not optimal --- it's not optimal for CPUs, and it's not optimal for drives. It is, however, easy to fix in drives, harder in CPUs. The problem is streaming data. With the model described above, any sort of operation that performs a one-time run through a large file (copying/backup, or just watching a movie) is going to replace the entire cache with one-time data. I don't know what the standard ways to deal with this are, but I have an easy solution which is that, associated with each way is a small amount of RAM that stores the most recently seen blockID as a POTENTIAL candidate for the cache. So at any given time, a way contains, say, 4 blocks of good data, plus the ID of the most recent block mapped onto that way which did not hit in the cache. If the next block that does not hit in the cache is the SAME as the potential candidate, we treat that as a verification that we are not streaming, and the on this second read we move the block into the cache.

You can expand this idea, based on real-world data, to whatever works best. In particular, this scheme as exactly described is potentially fragile in that it requires two successive reads to the same block (within a particular way) without an intervening read elsewhere in the way. So it is good at keeping out streaming data, but potentially also keeps out some re-used data. You can deal with this by having the per-way pool of potential blockIDs be 2, or 3, or N in size --- when the pool is N in size, we can allow up to N-1 reads in that way to intervene between two successive reads to a block, and still catch the block.

So there is scope for some ingenuity in quite how these systems are designed. If I had to guess, my guess would be that the current system is something like 4-way associative. Not clear if they are using my idea (or some equivalent) to prevent streaming from screwing the system over. The test that should be done, which I don't see in the post, would be to time something like a bunch of app launches, THEN read 4GB sequentially from the disk, time the app launches again, and see if the time has gone down. It would not surprise me if this first round of firmware does little to nothing to prevent streaming pollution --- not least because the existing benchmarks are not testing for it. On the other hand, this also all suggests that there is scope, in time, for much better engineering to figure out the optimal number of ways for the cache, the optimal cache block size, and the optimal strategy to prevent streaming from polluting the cache.Reply

Bought drive in Nov 2010, started having issues with my Gateway 6864 FX not waking from sleep mode in Win7-64bit after 2 weeks. As it was past the 30 day NCIX return limit, I finally dealt with Seagate for a warranty exchange. Replacement drive worked fine for a week, then did EXACT same thing... only NOW my laptop refuses to boot or save my BIOS settings. CMOS clearing, different SATA drives and tech support visits to no effect; I now have a dead drive AND a dead laptop. Thanks for nothing, Seagate... not to mention the 60+ hours I've spent scouring forums, calling tech support and swapping drives. All because Seagate couldn't design a drive with APM that knew what it was doing.

While it WAS working, it woke from Sleep mode almost instantly and did indeed cut boot times by half. For general laptop use( no heavy video / encoding )it made things snappy.

Bottom line: DO NOT BUY this hybrid drive unless you are prepared for the consequences. Cutting-edge tech sometimes means you bleed, as is my case. I'm out $$ for the drive, and $$ for my was-perfectly-fine laptop that's now a brick and Seagate has no intention of doing anything except sending me ANOTHER one of these computer-killers in a box.

No thanks. I'll buy an SSD and keep backing up my data, like a wary consumer should.Reply

I'm curious why you are so confident that the problem originated with your Momentus XT and not with your laptop itself? While I suppose a drive could cause the problems you describe my instinct would be the exact oposite that the laptop fried the drive.

Personally I've had one of these for about a month and another for a few days (different laptops) and absolutely love this drive.Reply

Anand or anyone... I'm thinking about getting a OCZ V3 SSD (when available) for my new MBP arriving next week. The MBP is arriving with a 750GB 5400rpm drive which I'd thought about moving into drive caddy to replace the ODD. However, I'm wondering how much benefit there would be putting one of my 500GB Momentus XT's in the ODD bay instead of the 750GB HDD?

I've seen the amazing speed advantages using the Momentus XT as my boot drive (only drive) in my current laptops, but am wondering about it's performance when used as data drive. I imagine it'd be similar or even better, but thought I'd ask in case anyone knew better...

Finally, Anand, one thing that seems to be missing from all but the first test is how the performance changes over time as data ges cached by the HHDD (Hybrid Hard Disk Drive) and what you did or didn't do to standardize that performance. Reply

I read this long ago, probably a similar comment on here. But why even bother comparing to a 5400rpm hdd? The momentus XT runs at 7200rpm. I want to see it compared to a regular 32MB cache 7200rpm 2.5" hdd. My friends has a 7200rpm 2.5" drive in his Compal NBLB2 and it loads games and stuff REALLY fast. I have a striped RAID on my desktop and his laptop loads up League of Legends RIGHT after my desktop. My desktop was built in 07, but still. 2 7200rpm 3.5" drives in stripped RAID should blow his away... it doesn't.Reply

I think a lot of what we're seeing here, is simply a more modern 7200rpm 2.5" drive that just happens to hang with an older raptor. FWIR, the NAND speeds don't even really come into play during an instant performance test. It pulls frequently used data, and smaller files during normal desktop use. Over a few days to a week, you would see a performance increase in boot times, email, web browser startup, etc.. if these are the common apps you tend to use. Running CrystalDiskMark, HdTune, or HdTach only one time, would be mostly physical disk performance.Reply

I am not experienced in such things and hence seeking some help here. I want 500GB plus storage space in my MBP-2009 and SSD are way too pricy for that. This solution seems really good, but can some one tell if I can use this in my MacBook Pro (running the latest update of Lion)?

Any help is appreciated! Thank you...

Note: In their site they have a new 700GB version. Can I use that instead?Reply